The present invention relates to multi-peripheral-device enclosures, and, in particular, to a method and system for increasing the reliability and availability of a multi-peripheral-device enclosure by incorporating control elements for isolating components into the multi-peripheral-device enclosure and including redundant components, including redundant processor components that are interconnected by redundant busses and share in controlling other components of the multi-peripheral-device enclosure.
The fibre channel (xe2x80x9cFCxe2x80x9d) is an architecture and protocol for a data communication network for interconnecting a number of different combinations of computers and peripheral devices. The FC supports a variety of upper-level protocols, including the small computer systems interface (xe2x80x9cSCSIxe2x80x9d) protocol. A computer or peripheral device is linked to the network through an FC port and copper wires or optical fibres. An FC port includes a transceiver and an interface controller, and the computer peripheral device in which the FC port is contained is called a xe2x80x9chost.xe2x80x9d The FC port exchanges data with the host via a local data bus, such as a peripheral computer interface (xe2x80x9cPCIxe2x80x9d) bus. The interface controller conducts lower-level protocol exchanges between the fibre channel and the computer or peripheral device in which the FC port resides.
Because of the high bandwidth and flexible connectivity provided by the FC, the FC is becoming a common medium for interconnecting peripheral devices within multi-peripheral-device enclosures, such as redundant arrays of inexpensive disks (xe2x80x9cRAIDsxe2x80x9d), and for connecting multi-peripheral-device enclosures with one or more host computers. These multi-peripheral-device enclosures economically provide greatly increased storage capacities and built-in redundancy that facilitates mirroring and fail over strategies needed in high-availability systems. Although the PC is well-suited for this application with regard to capacity and connectivity, the FC is a serial communications medium. Malfunctioning peripheral devices and enclosures can, in certain cases, degrade or disable communications. A need has therefore been recognized for methods to improve the ability of FC-based multi-peripheral-device enclosures to isolate and recover from malfunctioning peripheral devices. A need has also been recognized for additional communications and component redundancies within multi-peripheral-device enclosures to facilitate higher levels of fault-tolerance and high-availability.
The present invention provides a method and system for isolating peripheral devices within a multi-peripheral device enclosure from the communications medium used to interconnect the peripheral devices within the multi-peripheral-device enclosure, and for isolating a multi-peripheral-device enclosure from a communications medium used to interconnect a number of multi-peripheral-device enclosures with a host computer. The present invention provides increased component redundancy within multi-peripheral-device enclosures to eliminate single points of failure to increase fault-tolerance and high-availability of the multi-peripheral-device enclosures.
Port bypass circuits are used to control access of peripheral devices to the communications medium used to interconnect the peripheral devices within the multi-peripheral-device enclosure. The port bypass circuits are themselves controlled by port bypass circuit controllers that can, in turn, he controlled by software or firmware routines running on a microprocessor within the multi-peripheral-device enclosure. These three levels of control facilitate intelligent management of peripheral devices, diagnosis of malfunctioning peripheral devices, and isolation of malfunctioning peripheral devices. The three-tiered port bypass circuit control is also extended to inter-multi-peripheral-device-enclosure connection ports, so that a malfunctioning multi-peripheral-device enclosure can be diagnosed and isolated from a communications medium connection the multi-peripheral-device enclosure to a host computer. Redundant port bypass circuit controllers and microprocessors can be used to improve reliability of the diagnosis and isolation strategies implemented using the three-tiered port bypass circuit control.
The present invention provides for redundant processors within a multi-peripheral-device enclosure and for a method by which the redundant processors can intercommunicate in order to share the task of controlling other components within the multi-peripheral-device enclosure. Inter-processor communications must be reliable and should not represent a potential single point of failure. Therefore, redundant serial buses are used to interconnect the processors. Inter-processor communication is implemented using mailboxes and callback routines. The processors divide control of components in the multi-peripheral-device enclosure so that a malfunctioning processor does not disable the multi-peripheral-device enclosure.